Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $86.51   8.685%   $94.0234   $94.02   $94.00   $94.00  
  Purchase #2 $147.25   8.453%   $159.697   $159.70   $159.70   $159.70  
  Purchase #3 $83.91   9.429%   $91.8219   $91.82   $91.80   $91.80  
  Purchase #4 $172.98   11.806%   $193.402   $193.40   $193.40   $193.40  
  Purchase #5 $193.98   5.179%   $204.0262   $204.03   $204.05   $204.00  
  Purchase #6 $44.87   3.787%   $46.5692   $46.57   $46.55   $46.60  
  Purchase #7 $66.43   6.858%   $70.9858   $70.99   $71.00   $71.00  
  7 purchase totals = $795.93       $860.5255   $860.53   $860.50   $860.50